Asking "why?" gets to the heart of an idea
"Why?" is one of the most powerful questions in my toolbelt of Mental acrobatics. Asking why forces you to question what you know and connect to broader contexts within your mind. If you imagine Conceptual space is like a landscape, this question can help explore the roots and landscape surrounding an idea and help to discover the deeper, more fundamental meanings underlying that idea.
To really delve to the heart of an idea, you must ask this question many times. Each time you answer, question your answer, and then question the answer that comes from that until you reach the limit of what you can answer. Through this process you can come across what I call "malleable truths", which can be applied to other ideas.
If your initial idea does not lend itself to asking why, let us take "tree" for example. First I must ask, "what is a tree?" before I continue questioning why is a tree. The fundamental ideas of a tree might be fundamental to all of life.
Learning to ask why has completely changed the way I think and write. To write an essay I will often take the core argument(s) and iteratively ask "why?" until I get to the deeper heart of what I'm trying to say, then use the last answer as the introduction and work my way towards the argument I started with.
I have experimented with using this technique in many contexts, for example: songwriting. Take any topic and delve into its deepest meanings with this technique and you will find an emotional foothold with which you can build a song.
Note: Toyota 5 whys follows a similar process